Comparison of Halogenation Potential Among Various Fractions of TOC in Water from Jingmi Canal, Beijing

Naturally occurring organic compounds in water from Jingmi Canal were sequentially fractionated into five fractions using filtration and adsorption columns of XAD-8 and XAD-4 resins in tandem: the fractions being particulates, hydrophobic compounds, humic substances, XAD-4 acids and other hydrophilic neutral solutes. Then each fractions was chlorinated simultaneously with sodium hypochlorite, and the dominant halogenated product determined in this experiment was chloroform. Brominated THMs were detected as well. Both TOC abundance and ratio of CHCl3 product to corresponding fraction of TOC showed that dissolved humic substances and particulate-adsorbed organics were the major precursors of chloroform. Low-molecular-weight hydrophilic XAD-4 acids also possessed noticeable halogenation activity. Other aquatic organic solutes, however, were relatively inert with respect to the three fractions mentioned above. These results suggested that in addition to humic substances, other potential precursors which have not been studied thoroughly before, such as XAD-4 acids, should be considered during water chloronation.